1. Field of the Invention
The present invention relates generally to a door latch for an electrical household appliance. Particularly, the present invention relates to a door latch for a laundry treatment appliance, for example a washing machine.
2. Description of the Prior Art
The door latch considered here is one of the so-called types with an indirect locking mechanism. Such a latch type has a gripping unit which serves to grip and retain a striker (or other closing body) as a door of the household appliance is closed and thereby hold the door closed. The gripping unit can be locked in a closed position by a plurality of mechanically series-connected arresting elements so that it cannot be opened. Each of the arresting elements can be displaced between two positions. A first arresting element can be moved into a position in which it effects a blocking of the gripping unit. After the first arresting element has moved into its position blocking the gripping unit, a second arresting element is in turn moved into a locking position in which it effects a blocking of the first arresting element so that this cannot move out if its blocking position. This corresponds to a closed and locked state of the door.
If the second arresting element is guided back out of its locking position into an unlocking position, the first arresting element is free again. This corresponds to a closed, but unlocked, state of the door. In this state, the gripping unit can drive the first blocking element out of its blocking position into a release position (typically in opposition to spring force) if the door is pulled in order to open it.
Typically, in the type of door latches considered here, an actuator is associated with the last arresting element in the chain of arresting elements and this can be used to move it between its locking position and its unlocking position.
For the prior art of such door latches with an indirect locking mechanism, please refer to WO 2011/132213 A1 and WO 2013/109585 A2.
According to WO 2011/132213 A1, a rotational body serving as a gripping unit is constructed with a so-called cavity into which a first arresting element dips as the door is closed. Inclined surfaces on the walls of the cavity and on the first arresting element ensure that a division of force takes place if an attempt is made to rip open the door when the door is closed and locked. Part of the force transmitted here from the gripping unit to the first arresting element is diverted directly into a housing of the latch by way of the first arresting element. Only a residual part of the force is transmitted from the first arresting element to a second arresting element which serves to selectively block the first arresting element.
According to WO 2013/109585 A2, a division of force does not take place between a gripping unit and a first arresting element, but between the first arresting element and an intermediate element which is seated in the force-transmission path between the gripping unit and the first arresting element. The intermediate element and the first arresting element are guided at a right-angle to one another, with a wedge-type engagement between both elements ensuring the desired division of force. If the door is pulled when it is closed and locked, the force acting on the gripping unit is transmitted via the intermediate element and from there into the first arresting element. The wedge-type engagement between the intermediate element and the first arresting element causes part of the force from the first arresting element to be diverted directly into a housing of the latch so that only a residual part of the force is transmitted further to a second arresting element serving to selectively block the first arresting element.
The solution according to WO 2011/132213 A1 is problematic in that the required cavity on the gripping unit is associated with a weakening of the material, which can have a disadvantageous effect on the load bearing capacity of the gripping unit.